Process for transferring gelatine silver bromide pictures



Patented July 7, 1931 MI [CHEL raooounnm-qoasn, OFPARIS, FRANCE,ASSIGNOB '10 SOCIETE iDE PHOTO- CHIMIE ELKA, OF NICE, FRANCE PROCESS FORTRANSFERRING GELATINE SILVER fiROHIDE PICTURES Application filed January31, 1927, Serial No. 165,038, and in France February 8, 1826.

It is known that an image on gelatine silver bromide layer developedwith certain developers which tan the gelatine in the presence ofnascent silver (especially pyrogallic acid slightly sulphited can betranserred to an surface, either at or cylindrical, and a erw ardsdeveloped with hot water to produce a gelatine relief corresponding tothe white parts of the picture photo- I 10 graphed.

The application of this principle to photomechanical processes has beenmade known by Koppmann but up to the present timegelatine-silver-bromide paper has not been used practically in thephotomech'anical industry except perhaps by direct inking of the papermore orless according to the Bromoil process, and by transferring theink upon the plate.

Numerous difficulties are met when trying to utilize the tanningproperties of pyro-' gallic acid or like developers when transportingand developing with the hot water the pictures themselves as pigmentarypictures.

The main difficulty consists in the fact that it is usually impossible,even in the most simple line pictures, to obtain in the spaces betweenthe portions or reserves of gelatine, a metal or the like (according tothe nature of the support used) which is quite bare and capable offirmly retaining the ink.

If the action of the tanning developer is pushed sufliciently far toobtain a picture sufficiently tanned to withstand hot water, even in thesmall isolated points of the reserve, then the transparent parts areequally slightly hardened, and especially in very narrow spaces it isimpossible to remove completely the gelatine. Otherwise stated it isimpossible to make use of the transfer of a picture having both fineblack and fine white details.

In the most favourable cases as when the picture is quite black andwhite, and when the emulsion diffuses very little while giving verycontrasty pictures which are free from fog, the metal or the othersupport is not perfectly bare, even though it is not possibleto detect,even by dyeing, any trace of gelatine in the parts from which thegelatine was washed out. Experiments show that the metal or the likeretains in its pores a little 'gelatinized water which prepares it inthe sulp uric acid for the removal of gelatine,

the ink first becomes removed from those parts where it would be thoughtthat the bare metal would be capable of retaining it.

According to the present invention, in order to remedy this defect, awell defined differentiation of the two gelatines is obtained (tannedgelatine and tender or non-hardened gelatine) whereby the tendergelatine is as far as possible removed, while almost perfect bareportions can thus be formed on the support in the spaces of thereserves.

For this purpose development is carried out in two stages, i. e. a firstpartial development with a tanning developer, completed by a developmentwith an ordinary develo er.

hen a picture, suitably taken on gelatine bromide aper, has beendeveloped up to about hal intensity with a tanning developer (pyrogallicacid slightly sulphited for example) then if development is brought tocompletion with a second strong developer not possessing tanningproperties (diamido-phen01, mono ethyl-p-amino-m-cresol sulphate(metol), hydroquinone or the'like, and even pyrogallic acid normally.sul hited) the silver reduced by this second eveloper in the presenceof the pyrogallic acid remaining in the layer, accelerates the tanningof the picture which takes place much more rapidly without hardening thetransparent parts of the picture. The picture can then be transv ferredon to metal, for example, exactly as a carbon picture, and bare metal inthe spaces of the resist can be obtained much more easily.

If however necessary, it is very easy to clean off the metal or othersup ort in the transparent parts of thefilm (w en for example thegelatine of these trans arent parts has been very slightly harden inspite of the two stage development), by rubbing the surface of the platewith a pad of cotton wool impregnated with a slightly abrasive mixture(a cream of Spanish white in alcohol or the like), this cleaning can beeffected very easily and rapidly.

This cleaning, which is however not absolutel necessary with theaforesaid twostage evelopment, may alone sufiice in certain cases, asfor example with lines of mediuni fineness, to render the metal bare inthe spaces of the substance so that the process will then become asimple ordinary tanning development.

When fine drawings are in question however, it is necessary to developin two stages as indicated above, with or without subsequent cleaning.

Whatever the procedures adopted, the plate may then be treated by anyknown process of inversion. It may for example be inked up, the gelatinethen removed with a soft brush in a very weak bath of sulphuric acid forexample, leaving a transfer with the greasy inks which is inverse to thefirst image and is therefore black and white as in the picture which wasphotographed. These transfers can be used for lithographic printings orbe engraved as typographic plates by all known processes.

It is to be noted further that the two-stage development process, whichis the subject of this invention, allows further advantages to beobtained by overcoming the secondary phenomena of silvering frequentlyoccurring eretofore.

Experiment shows that when the usual fixing following a tanningdevelopment is not pushed much be ond the moment in which the whiteimage as disappeared, the soluble silver salts remaining in the layerwill give silver stains on zinc, beneath the black ortions as well as inthe transparent parts 0 the picture. Now nascent silver also possessestanning properties under these conditions, and the soluble gelatine willbecome insoluble at the places where such stains exist.

These defects are easily avoided when the ordinary fixing process isreplaced by a nontannin develo ment in day-light or white light, t uspro onging the two-stage development described whereby the bromidepicture is masked by a thorough blackening.

One may, for example, after com letely de veloping the picture in thesecon ordinary developer, continue development with white light, u tocomplete blackenin of the material. Washing will then su cc to avoidsecondar tanning phenomena due to the silvering o the metal.

As the gelatine which has remained soluble is now strongly coloured, itsremoval with hot water is more easily effected.

In order to make the steps of my process clearer, reference is made tothe accompanythe emulsion layer 6, a portion of which,

within the bracketed zone 0, is represented as having been treatedaccording to the process. (1 are the grains of silver bromide which aremore or less enlarged and condensed according to the stage ofdevelopment, and the crosses e are the oxydizing products which remainafter the action of the developer. The hatching f shows the tanned partsof the layer. I

Fig. 1 shows the plate as it appears after the first (tanning)development has been partially carried out. The grains of silver (Z aresmall and spaced and the oxydizing products e are present in the zonebut their action is notsuflicient to render the gelatine insoluble. v

Fig. 2 shows the same part of the plate after the second developmentwith ordinary developer has been carried out to a certain degree. Thissecond development has considerably increased the mass of the reducedsilver and the amount of the oxydizing roducts ofthe tanning developmentis su cient to insolubilize the gelatine.

Fig. 3 shows the same portion of the plate after the second developmenthas been com pleted. It will be seen that the reduced silver isdispersed and is present everywhere. The paper is black everywhere butthe gelatine is tanned only where the first development left oxidatedresidues. Elsewhere the gelatine remains soluble in hot water.

In a process according to the invention it may be desired to color thesensitive layer more or less with colours which do not act on thebromide (Congo red or the like) in order to limit the phenomena of thediffusion of the light in gelatine which hinders the production of finedetails in the picture, and thus to increase the resolving power of theemulsion.

In the preceding, where metallic or like supporting plates have beenspoken of, it is understood that there may also be used metallic platesalready covered with a reserve varnish on which the gelatine transferallows of local action by dissolving.

Naturally also the reserves of gelatine obtained can be strengthened byproducing ozobrome pictures at their surfaces.

Finally, it is also evident that all gelatine silver bromide papers canbe used for carrying out this invention.

Among the application of this invention, may be mentioned, among others,the reissue of texts and music scores, as also transfers on metal oftexts and of music composed with the aid of machines using photography.

What I claim is:

1. In a process for transferring gelatine silver-bromide pictures, thesteps which comprise first partly develo ing the picture with a tanningdevelo er an then continuing the development wit an ordinary non-tanningdeveloper.

2. A process for transferring gelatine silver bromide pictures asclaimed in claim 1,

m in which the operation of double developing of the picture isprolonged by a. non-tanning developing in white light, to obviatesecondary tanning efiects caused by silvering of the metal.

3. Process as claimed in claim 1 in which a sensitive layer of gelatinebromide tinted with a colour having no action on the bromide isemployed, whereby difiusion of light in gelatine is eliminated and itsresolving power increased.

4. In a process for transferring gelatine silver bromide ictures thesteps which comprise first partlally developing with a tanningdeveloper, then with an ordinary developer, continuin the seconddevelopment in white light, inking the plate and after removing thegelatine as for an inversion, resining and heating the ink and treatingwith acid to obtain a first relief.

5. In a process for transferring gelatine silver bromide pictures, thesteps which comprise partiall developmg the picture with a tanning deveoper and then continuing and completing the development with anon-tanning developer.

I In testimony whereof I have afiixed'my signature.

MICHEL PROCOUDINE-GORSKY.

